Numerous marine vehicles operate in shallow and restricted waters where maneuverability is a primary safety concern. Pushboats, Towboats, and Tugboats are some of the most common marine vehicles that navigate shallow waters and waters with strong currents. The maneuverability of a marine vehicle affects the safety of crew members, cargo, the marine vehicle itself, and the same within the vicinity of the marine vehicle. Furthermore, maneuverability is an integral component of the transportation efficiency of particular marine vehicles speed and fuel consumption. Because marine vehicles, such as tugboats, move large loads over great distances, they consume thousands of gallons of fuel in any operating year. Thus, by increasing the maneuverability and/or agility fuel consumption can also be decreased.
Presently the majority of tugboats rely on a conventional rudder system with a propulsion system forward of a single rudder or a single flapped rudder that is centered relative to the propulsion system. Many tugboats may have two propulsion systems, each having a single corresponding rudder that is flapped or unflapped. This current configuration has limited maneuverability, side thrust capabilities, and limited versatility as the rudder is large in both length and height relative to the propulsion system. These limitations, and others, limit significant numbers of marine vehicles from operating in shallow waters. These limitations also hinder the maneuverability and fuel efficiency of those marine vehicles.
Applicant believes at least one reason single rudder systems suffer from the aforementioned deficiencies is that in any one turning position a single rudder is only capable of diverting a portion of the jet stream. That is to say, that when the rudder pivots, a significant portion of the output power from the propulsion system (jet stream) will not make contact with the rudder. In turn, the output power from the propulsion system (jet stream) flows past the rudder without being fully utilized for maneuvering purposes. This phenomena explains at least one reason why embodiments in accordance with the present disclosure exhibit significantly higher “lift” relative to the prior art.
While some marine vehicles have a “dual rudder system” with a propulsion system forward of a pair of rudders these rudders each turn symmetrically with respect to one another in any one position. This type of configuration has limited maneuverability, side thrust capabilities, and limited versatility. The present disclosure is directed to a dual differential rudder system in which the rudders turn at different angles relative to one another. That is to say, the present disclosure is directed to navigation systems with two propulsion means, each propulsion means having a pair of rudders that turn at different angles relative to one another. Applicant has discovered, through extensive fluid dynamic testing and modeling, that embodiments in accordance with the present disclosure exhibit significant increases in maneuverability and fuel efficiency.
Applicant believes at least one reason the presently claimed dual differential rudder system is superior to conventional dual rudder systems is that the presently disclosed dual differential rudder system allows each rudder to turn at differential angles relative to one another. For example, when turning hard left the starboard side outermost rudder may turn at 36° while the interior most rudder may turn at 44°. That is to say, that when a dual differential rudder system pivots, each rudder turns at a different angle relative to the central neutral position. This unexpected phenomena explains at least one reason why embodiments in accordance with the present disclosure exhibit significantly higher “lift” relative to the prior art.
The present disclosure addresses one or more of the problems set forth above and/or other problems associated with conventional steering systems and rudders. The disclosed devices, methods, and systems are directed to overcoming one or more of the problems set forth above and/or other problems of the prior art, namely improving the maneuvering ability, fuel efficiency, and versatility of marine vehicles in navigable waters; particularly in shallow waters with strong currents.